Each of the projects include as a component the design, study, or use of gene targeted as well as normal mice or mouse tissues. The aim of the core is to centralize and coordinate these activities, with streamlined generation of gene targeted chimeras, generation of mutant stocks, and histological analysis of mutant tissues. In this way all techniques relating to ES cell work, mouse stock maintenance, and tissue harvesting and analysis will be performed by a small number of people using standardized methods, under the supervision of a PI with specific experience in the field.